Local area networks (LANs), such as are used, for example, in computer communications, are well-known and described in U.S. Pat. No. 5,041,963, entitled, "Local Area Network with an Active Star Topology Comprising Ring Controllers having Ring Monitor Logic Function," by Ebersole et al., issued Aug. 20, 1991; U.S. Pat. No. 4,998,247, entitled, "Active Star-Configured Local Area Network," by Irvine-Halliday et al., issued Mar. 5, 1991; U.S. Pat. No. 4,982,400, entitled, "Ring Bus Hub for a Star Local Area Network," by Ebersole, issued Jan. 1, 1991; U.S. Pat. No. 4,825,435, entitled, "Multiport Repeater," by Amundsen et al., issued Apr. 25, 1989; U.S. Pat. No. 4,872,158, entitled, "Distributed Control Rapid Connection Circuit Switch," by Richards, issued Oct. 3, 1989; U.S. Pat. No. 4,787,082, entitled, "Dataflow Control Arrangement for Local Area Network," by Delaney et al., issued Nov. 22, 1988; and U.S. Pat. No. 4,674,085, entitled, "Local Area Network," by Aranguren et al., issued Jun. 16, 1987; all of the foregoing being incorporated by reference.
The stations or nodes of a local area network may be configured in a variety of shapes, such as, for example, as a ring or a star. In a star-configured or local area hub network, multiple, discrete, remote stations are coupled through a central site or station, termed a hub station. The hub station must then follow a particular or predetermined signaling protocol to establish communications and to determine the order in which remote stations are permitted to transmit data over the network in the form of signals, such as electrical or optical signals. In one such signaling protocol, termed round robin, each of the remote stations is separately polled for transmissions. Likewise, in a round robin signaling protocol, only one station may transmit electrical signal data over the network at a time.
As disclosed and described in Draft for Standard Information Technology Local and Metropolitan Networks- Part 12: Demand Priority Access Method and Physical Layer Specifications, P802.12, dated March 1994, herein incorporated by reference, a round robin protocol has been proposed to the IEEE to be employed in local area networks transmitting data in the form of electrical signals at 100 megabits, termed 100 base VG. A round robin protocol provides advantages over other known network protocols, such as the protocol employed by IEEE standard 802.3, also known as CSMA/CD (Carrier Sense Multiple Access with Collision Detector), such as, for example, 10 base T, particularly for multimedia communications tasks that may be time sensitive. For such multimedia tasks or applications, it becomes desirable to prioritize or control access to the media or communications network provided different remote stations, such as computer peripherals, so that, in general, the more important communications tasks obtain access to the network earlier than the less important tasks.
For a local area hub network, it often becomes desirable to increase the size of the network without substantially degrading signal transmission performance; that is, it is desirable for the network to be extendible. However, as local area hub networks increase in size, the hardware for communications between remote stations of the network becomes increasingly complex. For example, technological limitations on the manufacture of integrated circuit chips typically restrict the number of ports that may be fabricated on one chip. Thus, for a large local area hub network having, for example, tens or hundreds of stations, communications between the remote stations directly linked or coupled to one hub station in the network may need to be shared among several, discrete devices or chips. The problem of performing or controlling round robin polling between these discrete devices also becomes more complex. Thus, a need exists for a method of polling remote stations for an extendible, round robin, local area hub network.